title: Comparative study of SoxR activation by redox-active compounds.
abstract: SoxR from Escherichia coli and related enterobacteria is activated by a broad range of redox-active compounds through oxidation or nitrosylation of its [2Fe-2S] cluster. Activated SoxR then induces SoxS, which subsequently activates more than 100 genes in response. In contrast, non-enteric SoxRs directly activate their target genes in response to redox-active compounds that include endogenously produced metabolites. We compared the responsiveness of SoxRs from Streptomyces coelicolor (ScSoxR), Pseudomonas aeruginosa (PaSoxR) and E. coli (EcSoxR), all expressed in S. coelicolor, towards natural or synthetic redox-active compounds. EcSoxR responded to all compounds examined, whereas ScSoxR was insensitive to oxidants such as paraquat (Eh -440 mV) and menadione sodium bisulphite (Eh -45 mV) and to NO generators. PaSoxR was insensitive only to some NO generators. Whole-cell EPR analysis of SoxRs expressed in E. coli revealed that the [2Fe-2S](1+) of ScSoxR was not oxidizable by paraquat, differing from EcSoxR and PaSoxR. The mid-point redox potential of purified ScSoxR was determined to be -185 ± 10 mV, higher by approximately 100 mV than those of EcSoxR and PaSoxR, supporting its limited response to paraquat. The overall sensitivity profile indicates that both redox potential and kinetic reactivity determine the differential responses of SoxRs towards various oxidants.
authors.affiliation: Laboratory of Molecular Microbiology, School of Biological Sciences, Institute of Microbiology, Seoul National University, Seoul, 151-747, Korea.
authors.forename: Atul K
authors.initials: AK
authors.lastname: Singh
authors.forename: Jung-Ho
authors.initials: JH
authors.lastname: Shin
authors.forename: Kang-Lok
authors.initials: KL
authors.lastname: Lee
authors.forename: James A
authors.initials: JA
authors.lastname: Imlay
authors.forename: Jung-Hye
authors.initials: JH
authors.lastname: Roe
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D016877:Oxidants / Q000378:metabolism*; D010084:Oxidation-Reduction; D010269:Paraquat / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D026361:Reactive Nitrogen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D048372:Streptomyces coelicolor / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D013447:Sulfites / Q000494:pharmacology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D024483:Vitamin K 3 / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D016877:Oxidants; D026361:Reactive Nitrogen Species; D013447:Sulfites; D015534:Trans-Activators; D014157:Transcription Factors; C070724:SoxR protein, Bacteria; C070725:SoxS protein, E coli; D024483:Vitamin K 3; D010269:Paraquat; C009279:sodium bisulfite